Horn antenna system



Mmh4,1947. .icack'ngp i 2,416,675

i HORN ANTENNA SYSTEM Ac. BECK WVEVTORS-H r FR//s 4 Arron/v5? March4,1947. Aye, BECK'ETAL 2,416,675 'I HORN ANTENNA.y SYSTEM Filedl Nov.2e, 19211` s .sheets-sheet 2 ATTORNEY Maich 4, 1947. A. c. BECK Em.2,416,675

` Holm 'ANTENNA SYSTEM maur/c uw f DIRECT/01ML CHMCTI'RISTK Il PLNE a'LONG! TUD/NAL AXIS 'f' ELECTRIC PLANL ATTORNEY Patented Mar. 4, 1947.www

A'hl-{()RN ANTENNA SYSTEM Alfred C. Beck, Red Bank, andy Harald T.Frlls, Rumson, N. J., asslgnors to Bell Telephone Laboratories,Incorporated, New York, N. Y., a

corporation of New York Application `November 26, 1941, Serial No.420,454

This invention relates to antenna systems and more particularly toultra-short wave and microwave horn antenna systems.

As is known, horn antennas for projecting or collecting radio energy ina fixed unidirection coinciding with the longitudinal horn axis, andhorn antennas associated with deflectors for securing omnidirectional ornon-directional `radio action in a plane perpendicular to the longitu-ndinal axis, have been suggested for use in the ultra-short wave (belowmeter wave-length) and the microwave (below 1 meter) elds. For example,United States Patents 2.206,923 and 2,369,808, both granted to G. C.Southworth, and British Patents 534,066 and 534,067, W. L. Barrow, bothcomplete accepted February 26, 1941, disclose horn antennas and hornantennas asso' ciated with deiiectors. In most of the horn antennasystems heretofore proposed for propagating energy unidirectionally, thewave front is not at since the diverging wave paths extending from thehorn throatl aperture to the horn mouth aperture, are unequal in lengthwhereby the wave components in the plane of the mouth aperture are toAsome extent in phase disagreement. It now appears desirable to securephase agreement among the wave components propagated in the samedirection and to improvev greatly the. operation of unidirectional hornantennas. Moreover, it is now desirable to project or collect radiantenergy, unidirectionally in a plane perpendicular to the longitudinalhorn axis, and to control accurately the unidirectional action of hornantennas especially horn antennas having relatively large dimensions. 4

It is one object of this invention to project and collect, in a hornantenna. system, only in-phase vx-.ve components in a given singledirection.`

It is another object of this invention to steer or control the directionof maximum radiant action of a large antenna in a simple mannerutilizing a minimum of equipment. l l

It is still another object of this invention to deflect or direct allthe wave energy emitted by a horn antenna along a single path,substantially, included in a plane perpendicularly related to thelongitudinal horn axis.

It is a further object of this invention to project or collect radiowaves unidirectionally in ya- 'horizontal plane utilizing a verticalhorn antenna and relatively simple supporting structure.`

It is still another object of this'invention tol project or collect, ina'slngle'point `direction included in a horizontal plane. eitherhorizontally 14- Claims. (Cl. Z50-11) or vertically polarized wavesutilizing the same vertical horn antenna. v

According to one embodiment of the invention a. plane or paraboloidalunipoint, directional deector is attached to one mouth aperture edge ofa large vertical horn antennahavlng a'square transverse cross section,for projecting or collect-k ing energy in a single direction in ahorizontal plane. The paraboloidal deiiector has a circular' contour inthe wave 'front plane and a parabolic contour in the wave propagationplane. the wave front plane being perpendicular to the wave directionand the propagation plane being perpendicular to the wave front planeand including the wave direction. The horn sides or walls adjacent thedefiector are in effect continued to the de` ilector and the extendedside portions function as shields to confine the radiation or collectionto the given horizontal unipoint direction, the

defiector aperture facing, of course, the desired horizontal directionof action. The hom may-'ber self-supporting or it may be mounted in acribi or cradle having a pivot, or point support'g-thehorn being held ina vertical position by` means of four guy cables attached to thecornersoffthe mouth aperture. PreferablyturnbuclclesiaeprolI vided inthe guy cables for the purpose fpermit' ting tilting oi the horn in thevertical plane vand' slight twisting or rotation about, .the vertical orlongitudinal horn axis. The hornis connectedto a horizontal waveguideline through a straightv throat section or twisted throat,vsection, dev pendent upon the plane of wave polarization desired and thedirection of extension of the -line relative to the front side of thehorn.

The invention will be more fully understood' from the followingspecification taken in con junction with the drawing on which likereference characters denote elements of similar function and on which:

Fig. 1 illustrates a horn-deflector antenna-system constructed inaccordance with the inven-y tion; Figs. 2, 3 and 4 are respectivelyside, front and top cross sectional diagrammatic views used inexplaining the operation of the system of Fig. 1: Figs. 5 and 6illustrate, respectively, a twisted horn throat section and a planelreflector which may be substituted in the system'of Fig. 1 for thestraightf throat section and paraboloidal reflector.' and Figs. 7 and 8are directive diagrams for 'the system of Fig. 1 modified to include theplane reector of Fig. 6.

Referring to Fig, 1, reference numeral l desig nates a vertical hornantenna' comprising ve horn sections 2 and having a'front wall 3, backvanized zinc.

wall 4, side walls 5, a transverse graduated cross sectional area 6, alongitudinal axis 1, a mouth aperture 8, a throat aperture 9 and anoptimum ratio of horn length to horn mouth aperture area, the lengthbeing measured along the axis 'l between the mouth aperture 8 and thethroat aperture 9. The horn proper .isian inverted square pyramidallstructure having avirtual y apex III. The throat aperture 9 isconnected through cou'- pling sections II and I2 to a wave guide I3 anda translation device I4 which may be a transmitter or receiver. As isshown on the drawing, the cross sectional area of the section I2 isrectangular whereas the cross sectional area of section I I changesuniformly from rectangular to square. As used herein, the termrectangular denotes a rectangular configuration other than square, andthe generic term "quadrangular signifies rectangular or square.

Reference numeral I5 designates a paraboloidal dei-lector attached tothe back edge I6 of the horn mouth aperture 8 and to the extended wallportions or shields Il, the deector being positioned, as is explained inmore detail below, so

as to face both the throat aperture 9 and the wall opening I3 formed inthe plane of the front wall 3 by the front edges I9 of the shields I'I,the front edge of-the deflector I5, and the top edge 2li of the frontwall 3. Thehorn I and deflector I5 are preferably of light weightconstruction as, for example, wood, the inside surfaces being lined withcopper-coated paper or gal- The opening I8 may, if desired, be equippedwith a plywood cover 2I for weather protection. The horn sections 2 andthroat sections II and I2, are preferably detachable so that they may benested for the purpose of facilitating transportation.

The lower portion of horn I is symmetrically included within themetallic or wooden cradle structure 22 whichis mounted on the pivot orpoint support 23 and ground plate 24. The corners 25 of the mouthaperture 8 are each connected to the ground 26 by a separate guy cable21. Each guy cable includes a turnbuckle 28 which permits a certainamount of movement or twisting of the horn I about its longitudinal axis'l and substantial rotation or tilting about the pivot support 23 in theplane of the wave direction 29 and the axis 1, whereby the effectivedirection of radio action of the system may be steered or aligned with adesired path of propagation.

Referring to Figs. 1, 2, 3 and 4, the defiector I5 has, in the movingvertical plane 30 of the wave front, a circular contour represented bythe curved lines or arcs BB', CC', DD' RR', Fig. 3, with centres on aline 3i', Fig. 2, passing through point A. Point A is located at thevirtual apex II) of the horn. In the vertical plane 32 of wavepropagation, the deflector has a parabolic contour BJR, Fig. 2, thevfocus of the parabolic curve being also at A. In Fig. 2, the plane 30 isperpendicular to the paper and includes points S and C and the plane 32includes the paper and points A, B, R, S, and C. In Iother words, thedefiector I5 is a paraboloid nf revolution and resembles a portion ofanautomobile headlight reflector. As shown by Fig-3, a longitudinal crosssection of the horn and attached deector, taken in the plane 39 of thewave front. is sectorial. The parabolic curve or contour is expressed bythe following equation for polar coordinates '1-I-sin a 4 where edge AB.

As illustrated by Fig. 2, the diverse bent paths ABC, ABE, AFG ARSincluded in the plane of propagation 32 and extending from the virtualapex I0 via the deflector I5 to the plane 30 of the desired wave front,have by virtue of the position and shape of the deflector I5, equallengths. In any of the planes ABB', ADD', etc., Figs. 3 and 4, whichplanes are in quadrature `to plane 32, the diverse paths as, forexample, AV

and AW, are equal and the right-angle extensions VV' and WW of thesepaths to the desired wave front 30 are also equal.

In operation, Fig. 1, assuming the system is used for transmission,energy from the transmitter I4 is supplied by the rectangular wave guideI3 to the horn I and the wave components are propagated along thediverging paths within the horn I. After passing through the mouthaperture 8 the waves impinge upon deector I5 and thence are directed ordeflected through the wall opening I8 in a substantially horizontaldirection 29. Since the lengths of the diverse'paths in the plane 32extending from the throat aperture 94 to the desired wave front 30 aresubstan` tially equal, the wave components or `waveletsin the. verticalwave front plane 30 are in phase vand combine to produce a maximum eectin the cal reasons at some sacrifice in operating eifectiveness. Thepredominating wave propagated inside the wave guide I3 and supplied tothe horn I is, as is well-known, polarizedin a direction coinciding withthe short transverse dimension as shown by arrows 33, Fig. 1. Hence,with the wave guide connected so as to extend in a frontto-back linedirection relative to the horn, as

shown in Fig. 1, the wave impinging upon de-A ector I5 is, immediatelybefore intercepting the deiector, polarized horizontally in the verticalplane of propagation 32' and after reflection is vertically polarized insaid plane as shown by arrow 34 in Fig. 1.

Referring to Fig. 5, numeral I2' designates atwisted throat sectionwhich `may be used in place of the straight throat section I2 includedin th'e system of Fig. 1 for rendering the polarization of the emittedwave horizontal. To make the conversion, section Il shown in Fig. 1 isrotated as shown in Fig. 5, and the twisted throat section I2' is thenfitted between horn section II and the wave guide I3. In operation,

the twisted throat functions to rotate the polarization plane of thewavelets propagated within the horn 90. the wave after passing throughthe twisted throat section vbeing horizontally polarized in a verticalplane perpendicularlyrelated tothe vertical propagation plane 82.

As a result, the polarization of the wave is reversed or changed 180 bydeflector I5 but, as emitted through the aperture I8 in wave propagationdirection 29, the wave is horizontally polarized, Thus, the same hornantenna system may be employed for' emitting or receiving eithervertically polarized or horizontally polarized waves in a givenpropagation direction. As analternative, the line I3 may extend in aside-to-side.

line direction, that is. in a direction making a right angle to thedirection shown in Fig. 1, the

section` II being oriented as shown vin Fig. 5. With thismodificationthe straight section I2 is employed to `produce horizontallypolarized waves and the twisted section I2' to produce verticallypolarized waves.

than the paraboloidal assembly. In operation,

, 'l2 (Fig. 7) and curves 80, 8i and 82 (Fig. `8)

represent, respectively, the directiveV` characteristics of a verticalhorn not equipped with a deflector assembly, a horn antenna having aplane reflector I5" but not shield members I 'l', and a horn antennaequipped with a plane deflector Vand shield members, as illustrated byFig. 6.

Fig. 'l represents the magnetic plane directive characteristic and Fig.8 represents the electric plane characteristic.A As may be' seen by comparing curves land 1I, and 80 and 8l, the open deflector I5' functionsto change the direction of maximum radio action 90. Also as may be seenby comparingcurves 1I and 12, and curves 8i and 82, the shield membersI'I increase thev sharpness of the directional effect and prevent oreliminate the minor lbes as, for example, lobe 83.

Although the invention has been explained in connection with certainembodiments, it is to be understood that it is not to be limited to theap-` paratus illustrated, inasmuch as other equip-- ment and apparatusmay. be satisfactorily em-I ployed in practicing the invention.

What'is claimed is:

-1. A quadrangular horn antenna having me'- tallic walls each-of varyingwidth and an aperture in one wall at its wide end, said horn antennahaving a sectorial cross section. in the plane of said aperture.

y 2. A dielectric channelforconveying electrof magnetic waves, saidchannel having metallic walls and an aperture facing in a directionperpendicular to its longitudinal axis, substantially,

said channel having in a plane perpendicular to said direction andincluding vits longitudinal axis a cross-sectional area bounded by twoangularly related lines and a curvate line connecting said lines 'attheir widest separation.

3. .In combination, a metallic horn antenna having a longitudinal axisand a cuadrangular mouth aperture for propagating in a direction alignedwith said axis waves having a concavoconvex or curved wave front, saidhorn comprising four angularly related walls each having a metallicinner surface, a concave metallic deilector attached to' one edgeof saidhorn aperture and a separate plane metallic shieldattacl'ied to each`aperture edge radjacent said first-mentioned edge, whereby the waves arepropagated in a single direction substantially perpendicular to saidaxis and the curved wave front is changed to a'plane wavefront.-

4. A quadrangular metallic horn antenna hav-. ing a throat aperture anda side aperture in lits front wall, a metallic paraboloidal deilectorfacing said apertures and having a finite focus located on thelongitudinal axis of said horn. whereby the lengths of the wave pathsextending from the horn throat aperture to said side aperture via saidde ector are substantially y equal.

5. In combination, a vertical horn-shaped di" electric channel forconveying transverse electric microwaves, a metallic paraboloidalreflector attached thereto and facing the mouth aperture of said horn,the focal axis of said reflector being in a horizontal plane, the hornbeing included between the reflector surface and the reector focus, saidhorn having its longitudinal axis superimposed on 'a linearv pathextending between said focus and said surface, the length of the hornalong said longitudinal axis being shorter than said path, wherebyunidirectional action in the horizontal lplane is secured.

6. A horny antenna system lined with conductive material and having akrectangular cross section, one side of said horn being extended be'-yond and at an angle to the plane of the horn mouth aperture and thetwoA sides adjacent said first, mentioned 'side being extended so as totouch the extended rst side, whereby an aperture is formed in the planeof the remaining side.

7. In combinationfa metallic horn antenna havingits longitudinal axisaligned with a given direction, said horn having a throat aperture and arectangular mouth aperture, a metallic deilector attached to said hornalong one edge of the mouth aperture for confining the travel of wavesprojected or collected by said horn to a single direction,substantially, said deilector being included in aplane perpendicularlyrelated to said given direction, and a device for generating orreceiving radio waves connected to the throat aperture.

8. In combination with an antenna system comprising a horn and adeflector for project-` ing or collecting a maximum amount of radioenergy in substantially one point direction. perpendicular to thelongitudinal axis of said horn. means comprising a point supportingstructure for mechanically steering the direction of maxi imum action ofsaid system in a plane containing said horn axis and in a planeperpendicular tosaid axis. .v s l 9. A vertical horn antenna systemyhaving an aperture facing in a point direction included in a horizontalplane and-.means for adjusting or steering the directive characteristicof said horn comprising a point supporting structure for said hornantenna and adjustable guy wires extendandere ing from diilerent upperportions oi said horn .to the earth. 1

10. In combination, a metallic horn antenna having a square mouthaperture and its longitudinal axisA perpendicularlyl aligned with thedesired direction oi' radio action, a metallic deiiector facing themouth aperture of said horn, said deiiector having a circular contour inthe plane of said axis and a parabolic contour in the plane of saiddirection and having its focus on said longitudinal axis.

11. An antenna system ior projecting or coln lectlng wave components ina given direction,

' the system comprising a rectangular horn having` a. side aperture inits front wall 'and a throat aperture, a paraboloidal reflector facingsaid side aperture and said throat aperture, 'the reflector focus beinglocated on the longitudinal `horn axis and the distance between thefocus and 'the reector being greater'than the length of the horn asmeasured along s'aid longitudinal axis, the focal axis o! said reflectorbeing perpendicular to said longitudinal axis and aligned with saiddirection, whereby all of the wave paths extending from the throataperture via 20 Number said reflector to a plane perpendicular to saiddirection have equal lengths and the in-phase wave components emitted orcollected by said system are included inaplane.

12. In combination, a vertical horn antenna having a square mouth,y aunidirectional deflector attached to one edge of said mouth fo`confining the wave propagation to a single direction, substantially, ina horizontal plane, a

transmitter connected to a rectangular wave guide, a wave guide memberhaving at. one end a square cross section and at'the other end arectangular cross section .and connecting said wave guide to the hornthroat.

18. A combination in accordance with claim 12, the wave guide memberbeing linear along its longitudinal axis.

14. A combination in accordance with claim 12. the wave guide memberbeing twisted 90 degrees about its longitudinal axis.

ALFRED c. BECK. `HARALD T. Fans.

REFERENCES crrEn The following references are oi record ln the ille ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Proceedings of the I. R. E., v01.28,` No'. 3, Marchv 1940 (pages 13D-131).

